The present invention is designed to deal with two broad but distinct classes of vascular problems: (1) the maintenance of suffcient arterial flow to perfuse the tissues in the extremities; and (2) the maintenance of adequate venous flow and the prevention of stagnation and clot formation in the veins.
There are two sources of these two classes of problems and either can exist without the other or they can coexist.
The first class of problems, interference with arterial blood flow, is typically caused by atherosclerosis, either localized or diffuse.
Inadequate arterial flow can lead to such problems as pain upon exertion, slow healing of injuries, easy infection of minor injuries, breakdown of soft tissues leading to slow healing ulcers and in the extreme, gangrene, with resultant need to amputate the limb.
Currently available medical drug therapies for this condition are of limited value. Surgical procedures, including for example balloon angioplasty, are more frequently used to correct these problems.
The second class of problems, stagnation of blood flow in the veins may be caused by structural changes in the veins, by partial or complete failure of one or more of the patient's valves and or by inadequate muscular activity in the patient, since venous flow in the patient's limbs is to a large part due to the alternate compression and release of the veins caused by pressure exerted upon them by the muscles in the limbs.
Currently available device based therapies are limited to the second class of problems involving venous flow and consist of means to limit the cross-sectional area of the veins through the use of support garments, such as elastic surgical support stockings, or they seek to periodically compress the veins more completely through the application of intermittent pressure about the limb to collapse the veins and expel the blood from them. In some cases the pressure is applied as a pulsating wave through a series of pneumatically actuated cuffs, starting distally and moving proximally toward the patient's heart in an attempt to "milk" or expel the venous volume still more completely.
Prior art devices intended to alter the normal flow of blood in a patient's circulatory system are descibed in a plethora of previously issued patents, the following being exemplary: U.S. Pat. No. 3,101,085 issued to Murphy, Jr. on Aug. 20, 1963 which discloses an alternating tourniquet system to prevent excess blood from backing up into the patient's lungs when the left side of the heart is unable to pump the entire volume of blood getting to it; U.S. Pat. No. 3,811,431 issued to Apstein on May 21, 1974 which discloses a programmed venous assist pump; U.S. Pat. No. 3,892,229 issued to Taylor et al. on July 1, 1975 which discloses apparatus for augmenting venous blood flow; U.S. Pat. No. 3,942,518 issued to Tenteris et al. on Mar. 9, 1976 which discloses a therapeutic intermittent compression apparatus; U.S. Pat. No. 3,976,056 issued to Brawn on Aug. 24, 1976 which discloses an intermittent pressure pneumatic stocking; U.S. Pat. No. 4,030,488 issued to Hasty on June 21, 1977 which discloses an intermittent compression device; U.S. Pat. No. 4,054,129 issued to Byars et al. on Oct. 18, 1977 which discloses a system for applying pulsating pressure to the body; U.S. Pat. No 4,057,046 issued to Kawaguchi on Nov. 8, 1977 which discloses a blood circulation stimulator; U.S. Pat. No. 4,153,050 issued to Bishop et al. on May 8, 1979 which discloses a pulsatile stocking and bladder therefor; U.S. Pat. No. 4,206,751 issued to Schneider on June 10, 1980 which discloses an intermittent compression device; U.S. Pat. No. 4,269,175 issued to Dillon on May 26, 1981 which discloses method and apparatus for promoting circulation of blood; U.S. Pat. No. 4,311,135 issued to Brueckner et al. on Jan. 19, 1982 which discloses apparatus to assist leg venous and skin circulation; and U.S. Pat. No. 4,374,518 issued to Villaneuva on Feb. 22, 1983 which discloses an electronic device for pneumomassage to reduce lymphedema.
Many of the pneumatic leggings or boots disclosed in the aforementioned references are adapted to fit around the calf and foot of a patient's legs, such leggings being connected to pump apparatus which sends alternate intermittent pulses to each of the leggings to periodically compress and release the legs and thereby accelerate blood flow. Typically, a series of one-way valves is used in the leggings so that blood is permitted to move only in an upward direction toward the patient's heart and backflow is minimized or prevented.
Unfortunately, none of these prior devices are designed to provide significant benefit in cases of deficient flow due to arterial problems.
Accordingly, it is an object of the present invention to augment blood flow in spite of reduced arterial lumen size and to increase the total venous blood exchange such that the veins are substantially distended and collapsed with each pressure cycle rather than merely compressed from their normal condition to a minimally distended condition with each pressure cycle.
It is another object of the present invention to provide method and apparatus capable of boosting blood circulation in a patient's limb while waiting for collateral flow to develop.
It is still another object of the present invention to provide method and apparatus for accomplishing the foregoing treatment which are not painful to the patient, which are safe and simple to use, which are highly reliable, yet which are relatively inexpensive to manufacture.